LMH6553MR National Semiconductor, LMH6553MR Datasheet - Page 17

• Manufacturer Part Number: LMH6553MR
• Description: DIFF AMP, 900MHZ, 8PSOP, POWERWISE
• Manufacturer: National Semiconductor

Specifications of LMH6553MR

• No. Of Amplifiers: 1
• Gain Db Max: 1dB
• Bandwidth: 900MHz
• Slew Rate: 2300V/µs
• Supply Voltage Range: 4.5V To 12V
• Supply Current: 29.1mA
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Rohs Compliant: Yes

When using the LMH6553 in single-to-differential mode, the
complementary output is forced to a phase inverted replica of
the driven output by the common mode feedback circuit as
opposed to being driven by its own complementary input.
Consequently, as the driven input changes, the common
mode feedback action results in a varying common mode
voltage at the amplifier's inputs, proportional to the driving
signal. Due to the non-ideal common mode rejection of the
amplifier's input stage, a small common mode signal appears
at the outputs which is superimposed on the differential output
signal. The ratio of the change in output common mode volt-
age to output differential voltage is commonly referred to as
output balance error. The output balance error response of
the LMH6553 over frequency is shown in the Typical Perfor-
mance Characteristics section.
To match the input impedance of the circuit in Figure 3 to a
specified source resistance, R
The equations governing R
operation are also provided in Figure 3. These equations,
along with the source matching condition, must be solved it-
eratively to achieve the desired gain with the proper input
termination. Component values for several common gain con-
figurations in a 50Ω environment are given in Table 1.
FIGURE 3. Single-Ended Input with Differential Output
12 dB
12 dB
TABLE 1. Gain Component Values for 50Ω System
TABLE 2. Gain Component Values for 50Ω System
Gain
Gain
0 dB
6 dB
0 dB
6 dB
275Ω
275Ω
275Ω
325Ω
325Ω
325Ω
R
R
F
F
PSOP Package
LLP Package
54.9Ω
255Ω
127Ω
68.1Ω
IN
316Ω
150Ω
R
R
and A
G
S
G
, requires that R
V
for single-to-differential
68.1Ω
107Ω
56.2Ω
66.5Ω
110Ω
59Ω
R
R
T
T
T
|| R
26.7Ω
28.7Ω
26.7Ω
28.7Ω
34.8Ω
34Ω
IN
R
R
30043710
M
M
= R
S
.
17
The circuit shown in Figure 4 was used to measure S-param-
eters for a single-to-differential configuration. The S-parame-
ter plots in the Typical Performance Curves are taken using
the recommended component values for 0 dB gain.
SINGLE SUPPLY OPERATION
Single supply operation is possible on supplies from 5V to
10V; however, as discussed earlier, AC input coupling is rec-
ommended for low supplies due to input common mode limi-
tations. An example of an AC coupled, single supply, single-
to-differential circuit is shown in Figure 5. Note that when AC
coupling, both inputs need to be AC coupled irrespective of
single-to-differential or differential-to-differential configura-
tion. For higher supply voltages, DC coupling of the inputs
may be possible provided that the output common mode DC
level is set high enough so that the amplifier's inputs and out-
puts are within their specified operating ranges.
FIGURE 4. Single Ended Input S-Parameter Test Circuit
FIGURE 5. AC Coupled for Single Supply Operation
(50Ω System)
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